Arctic Kelp Forests Diversity, Resilience and Future

Global and Planetary Change 172 (2019) 1–14 Contents lists available at ScienceDirect Global and Planetary Change journal homepage: www.elsevier.com/locate/gloplacha Invited review article Arctic kelp forests: Diversity, resilience and future T ⁎ Karen Filbee-Dextera, , Thomas Wernbergb,e, Stein Fredriksenc, Kjell Magnus Norderhaugd, Morten Foldager Pedersene a Norwegian Institute for Water Research (NIVA), Gaustadalléen 21, 0349 Oslo, Norway b UWA Oceans Institute and School of Biological Sciences, University of Western Australia, Crawley 6009, WA, Australia c University of Oslo, Department of Biosciences, PO Box 1066, Blindern, N-0316 Oslo, Norway d Institute of Marine Research, Nye Flødevigveien 20, NO-4817 His, Norway e Department of Science and Environment (DSE), Roskilde University, DK-4000 Roskilde, Denmark. ARTICLE INFO ABSTRACT Keywords: The Arctic is one of the most rapidly changing places on Earth and it is a sentinel region for understanding the Seaweed range and magnitude of planetary changes, and their impacts on ecosystems. However, our understanding of Climate change arctic coastal ecosystems remains limited, and the impacts of ongoing and future climate change on them are Polar largely unexplored. Kelp forests are the dominant habitat along many rocky Arctic coastlines, providing struc- Sea ice loss ture and food for economically and ecologically important species. Here we synthesize existing information on Borealization the distribution and diversity of arctic kelp forests and assess how ongoing changes in environmental conditions could impact the extent, productivity, and resilience of these important ecosystems. We identify regions where the range and growth of arctic kelp are likely to undergo rapid short-term increase due to reduced sea ice cover, increased light, and warming. However, we also describe areas where kelps could be negatively impacted by rising freshwater input and coastal erosion due to receding sea ice and melting permafrost. In some regions, arctic kelp forests have undergone sudden regime shifts due to altered ecological interactions or changing environmental conditions. Key knowledge gaps for arctic kelp forests include measures of extent and diversity of kelp communities (especially northern Canada and northeastern Russia), the faunal communities supported by many of these habitats, and the role of arctic kelp forests in structuring nearby pelagic and benthic food webs. Filling in these gaps and strategically prioritizing research in areas of rapid environmental change will enable more effective management of these important habitats, and better predictions of future changes in thecoastal ecosystems they support and the services that they provide. 1. Introduction timing and magnitude of primary production, and driving shifts in the structure and function of marine communities (Grebmeier et al., 2006; The effects of humans are pervasive and are transforming natural Nelson et al., 2014). As a result, the entire Arctic region has been de- ecosystems and biogeochemical cycles on global scales (Halpern et al., signated an ocean warming hotspot (Hobday and Pecl, 2014). Impacts 2008; Waters et al., 2016). There is, however, great regional variation of rapid environmental change on arctic ecosystems has broad sig- in the nature, magnitude, and direction of these changes (Burrows nificance due to both the global uniqueness and large geographic extent et al., 2011; Krumhansl et al., 2016), and it is only by understanding of the region, and because they may act as a sentinel for other eco- these geographical intricacies that we can begin to grasp the full extent systems experiencing slower rates of change (Pecl et al., 2014; Hobday of our footprint on the planet. Currently, the Arctic is warming 2–4 and Pecl, 2014). Despite this, most Arctic coasts remain relatively un- times faster than the global average and is now one of the most rapidly explored, and the extent and resilience of coastal ecosystems are poorly changing regions in the world (IPCC, 2014). Marine ecosystems along understood, as are the ongoing and future impacts of climate change on Arctic coasts are experiencing increases in sea temperatures, dramatic them. Understanding changes to arctic ecosystems is especially critical declines in sea ice, and increased input of freshwater (Wassmann and because borealization (i.e., the northward shift of temperate commu- Reigstad, 2011; Coupel et al., 2015; Acosta Navarro et al., 2016; Ding nities) could squeeze out high arctic ecosystems altogether, resulting in et al., 2017). These changes are altering carbon cycling, affecting the the planetary loss of an entire climate zone (Fossheim et al., 2015; ⁎ Corresponding author. E-mail address: [email protected] (K. Filbee-Dexter). https://doi.org/10.1016/j.gloplacha.2018.09.005 Received 21 March 2018; Received in revised form 28 August 2018; Accepted 6 September 2018 Available online 12 September 2018 0921-8181/ © 2018 Elsevier B.V. All rights reserved. K. Filbee-Dexter et al. Global and Planetary Change 172 (2019) 1–14 Kortsch et al., 2015). conditions south of these limits (AMAP, 1998). Here we define ‘arctic Kelps are large brown seaweeds that occur on rocky coasts kelps’ as kelps occurring within the boundaries defined by the Arctic throughout the Arctic (Wernberg et al., 2019). Many (or most) kelps are Monitoring and Assessment Program (AMAP). AMAP originally defined important foundation species that create habitat (forests) for numerous Arctic boundaries in 1991 as regions north of the 10 °C July isotherm. fish and invertebrates (Christie et al., 2009; Norderhaug and Christie, These boundaries have since been expanded to include some areas that 2011; Teagle et al., 2017), provide food to marine communities through correspond to political boundaries of member nations of the Arctic high production and export of detritus and dissolved organic material Council (e.g., coastal shelf of Iceland, Norwegian northwest coast, (Krumhansl and Scheibling, 2012; Renaud et al., 2015; Abdullah et al., Hudson Bay, and the Aleutian Islands) (AMAP, 2017). We used this 2017; Filbee-Dexter et al., 2018 in press), and store and sequester definition because monitoring programs, assessments and decision- carbon (Krause-Jensen and Duarte, 2016). Currently, information on making on pollution and climate change in Arctic regions often use the distribution, diversity, stability, and function of kelp forests is AMAP boundaries. However, despite our inclusive definition of the missing for large portions of the Arctic (Wiencke and Clayton, 2009; Arctic, much of this manuscript focuses on kelp forests at higher lati- Krumhansl et al., 2016; Wilce, 2016). tudes within the AMAP region where kelps face the most extreme Arctic A recent global analysis of records of kelp abundance over the past 5 conditions and where globally unique species compositions are found. decades showed that kelp forests are changing in many regions of the world (Krumhansl et al., 2016). At the warmest edges of their range, 2.2. Distribution, growth forms and evolution of arctic kelps sudden shifts from kelp forests to reefs dominated by low-lying turf- forming algae have been increasingly documented over the last decade Although kelps range along most Arctic coasts, sparse records of (Filbee-Dexter and Wernberg, 2018). Along other temperate coasts, kelps in some parts of the Arctic have been attributed to a lack of hard native kelps are being replaced by invasive kelps or other seaweeds substrata (Kjellman, 1883; Wilce, 2016). Only about 35% of the Arctic (Wernberg et al., 2019), or are being heavily overgrazed by sea urchins basin is rocky substrate and shallow coastal areas and inner Arctic (Filbee-Dexter and Scheibling, 2014). In many of these regions, declines fjords are often dominated by sediment due to glacial run off and river in kelp abundance are partly explained by the direct and indirect effects deposition (Leont'yev, 2003; Lantuit et al., 2012), which limits the of warming sea temperatures (Ling et al., 2009; Catton, 2016; Filbee- presence of macroalgae. In areas with suitable substrate, dense kelp Dexter et al., 2016; Wernberg et al., 2016). Considering the widespread forests can extend from the intertidal zone down to depths of 30–40 m changes throughout the temperate and tropical range of kelp and the depending on light conditions, wave regime, and grazing intensity ongoing environmental changes occurring in the Arctic, the fate of (Wernberg et al., 2019). The deepest recorded kelp was observed at arctic kelps in this era of rapid change is a critical gap in our knowledge 60 m depth in Disko Bay, Greenland (Boertmann et al., 2013). In high of arctic marine ecosystems. Arctic regions, available light and sea ice further restrict this depth Here we synthesize existing information on the distribution, bio- range and the upper sublittoral zone is a barren, low salinity environ- mass, and dominant species of arctic kelp forests. We explore some of ment that is constantly impacted by sea ice and meltwater (Wiencke the services provided by arctic kelps and identify missing baseline and Clayton, 2011). measures of their extent. We analyze changes in the sea ice extent and The diversity of kelp in the high Arctic tends to be lower than in temperature conditions for known locations of kelp, and explore how temperate kelp forests (Wiencke and Clayton, 2011). Genetic evidence recent and future changes in these and other conditions could impact indicates that most kelps reinvaded

Load more